For water, at pressures below atmospheric;
A. Melting point rises slightly and boiling point drops markedly
B. Melting point rises markedly and boiling point drops markedly
C. Melting point drops slightly and boiling point drops markedly
D. Melting point drops slightly and boiling point drops slightly
Answer: Option A

Melting point rises slightly and boiling point drops markedly..We can easily understand from the pressure versus temperature diagram of water..Fusion curve for water is almost vertical so there is no any great change in melting point..But vaporisation curve is hyperbolic type do here is remarkable change in boiling point